We should mention GOOGLE_APPLICATION_CREDENTIALS in the Authentication section.

[aozarov]

The main gcloud-java README.md contains an authentication section however this section does not
mention the option of using the GOOGLE_APPLICATION_CREDENTIALS environment variable to point to a key file.

@mziccard I now wonder if we need the GCLOUD_TESTS_KEY and GCLOUD_TESTS_PROJECT_ID in the RemoteGcsHelper as GOOGLE_APPLICATION_CREDENTIALS could be used instead of the former and GCLOUD_PROJECT could be used instead of the latter.

[mziccard]

@aozarov When I introduced those 2 variables I took inspiration from gcloud-node. The rationale is that to run integration tests the user must know what he is doing and he has to pick the right credentials/projectId before running tests as he is going to be billed for them.

For instance I have a personal account on Google Cloud whose credentials are set in GOOGLE_APPLICATION_CREDENTIALS but I use different whitelisted credentials/project to run integration tests.

[jgeewax]

I'm with @aozarov on this one -- having separate env vars for tests seems a
bit off.

Running tests should look something like

$ cat run_test.sh
GOOGLE_APPLICATION_CREDENTIALS=test.json mvn test

right?

[aozarov]

Right, it should not be a problem to temporarily override environment variable.

[aozarov]

I created #335 for tracking the RemoteGcsHelper specific keys issue.